1. Field of the Invention
This invention relates to a device for applying and/or removing coatings on workpieces, said device having conveying means and a container (process chamber) for receiving the workpieces, an inlet line which is connectable to at least one medium source and an outlet line connecting the container to the medium source, said medium source disposed below the conveying means where the connection between the lines and the medium source is established by at least one control device which is connectable to at least three different medium sources and disposed below the container.
In conventional devices of the type mentioned above and as described, for example, in German Patent DE 10 34 447 B or British Patent GB 893 570 A, the medium is pushed into the process chamber. As a result, when media are changed, deposits remain in the conveying device and mix with the new medium. Thus, it is not possible to use these devices where a high degree of purity of the medium transported into the process chamber is required. A further disadvantage is that, if the lines are damaged, the media are conveyed to the outside under high pressure, due to overpressure in the lines and the process chamber.
Based on the above state of the art, it is an object of this invention to provide a device which operates without forming deposits and which can be used with incompatible liquids.
This object is attained in accordance with one embodiment of this invention wherein wherein the conveying means is a vacuum pump and is incorporated into the outlet line of the container (process chamber).
Accordingly, because the circulation of the liquid from the medium source to the container (process chamber) and back to the medium source is achieved by under negative pressure, at most an implosion may occur in the lines or reservoirs in the event of leaks. As a result, the medium does not reach the outside, but rather flows back into the associated medium reservoir by itself. In addition, during operation there are no noticeable disruptions of the operation, because switching occurs very rapidly. In this way, one continuous cycle is replaced by another continuous cycle in extremely short time.
In accordance with one embodiment of this invention, the conveying means is positioned above the medium sources. As a result all lines between the container (process chamber) and the medium, as well as the control means, for example radial or axial sliding valves, are completely emptied if they are not under pressure and they are connected to the respective medium reservoirs so that medium can flow through them.
In accordance with another embodiment of this invention, at least one opening for a holder supporting at least one workpiece is provided in the wall of the container (process chamber). The holder has an elastically deformable sealing section which is connected under pressure with the wall. In accordance with yet another embodiment of this invention, the opening is provided with a sheathing in the form of a truncated cone which tapers towards the interior.
This invention is applicable to and can be utilized, in particular, in the field of medicine, and more particularly, in the dental field. In embodiments of this invention suitable for such applications, the container (process chamber) comprises a material which is resistant to the media. Because the container (process chamber), is under negative pressure the plugs in the container do not require threads, it being sufficient to place them in the openings after they have been supplied with the workpieces. Because of the negative pressure, a force directed towards the interior of the container acts on the plugs and prevents their separation from the container.
Located between the conveying device and the container (process chamber) is a magnetic valve (V) which, when opened, equalizes the pressure so that the liquid can flow from the container (process chamber) and the lines into the appropriate medium reservoir without leaving a residue. Opening of the valve to the outside is regularly performed shortly before the end of one process step in which a particular liquid is used. When the valve has been closed again, a new and different medium flows into the container (process chamber). The plugs can be removed from the openings at the end of the entire process. In accordance with another embodiment of this invention, an entire wall in the container comprises a plate equipped with the plugs and workpieces and removable from the container (process chamber), which is then connected with the container (process chamber).
In a device for making electrolytically producible coatings on metallic bodies, the surfaces of the portions of the workpieces extending into the container (process chamber) are designed as a cathode or an anode, where an anode or a cathode is disposed opposite the workpieces and an electrolyte flows between the electrodes. To ensure that the inflowing liquid sufficiently bathes the workpieces, a device which affects the direction of flow of the liquid is disposed within the container (process chamber). In accordance with one embodiment of this invention the inlet line is connected to the bottom and the outlet line is connected to the top of the container (process chamber), the device comprises two plates, disposed at a distance from the bottom and the top of the container (process chamber), which cover the bottom or the top except for a gap or a slit in the area of the wall supporting the workpieces. This ensures that the incoming liquid flows along the inside of the wall supporting the work pieces and optimally bathes the workpieces.
In accordance with another embodiment of this invention, the a device is connected to an electrolyte reservoir as well as to pre-rinse and rinse water reservoirs it is advantageous, if an ion exchanger for the regeneration of the rinse water is disposed in the pre-rinse and rinse water reservoir. It is additionally preferred that two ion exchangers each be disposed in each reservoir. Such an ion exchanger comprises a hollow body, removably connected to the inlet or outlet opening of the reservoir and having an inlet and outlet opening, where means for absorbing ions are disposed between these openings. The advantage of this configuration is that the ion exchangers--once they are no longer fulfilling their function --can be removed from the reservoir and replaced by fresh ones. In this case the user of the device does not come into contact with any liquid.
This invention also relates to a method for applying and/or removing coatings from workpieces with a device as previously described. In accordance with the process of this invention the workpieces are disposed in the interior of the container (process chamber), the workpieces are pre-treated, if required. The control device is actuated so that an electrolyte or another chemical liquid flows through the container (process chamber). After a defined coating has formed, the control device connects the lines to a rinsing liquid which then flows through the container (process chamber).
Some exemplary embodiments of the invention are schematically shown in the drawings and will be described in detail below.